"I am not sure if she thinks that Jacinda is the Prime Minister of Sri Lanka as well as the Prime Minister of New Zealand.
"Katie Hopkins is a publicity seeker, and I hope that's the last time I say her name on TV."
Robertson said everyone should have the freedom to worship and follow their religious beliefs without the threat of being targeted.
"The fact is, it doesn't matter to me whether you are worshipping in a mosque or worshipping in a catholic church. You have a right to be able to do that and express your faith," he told the AM Show.
"In New Zealand, it was a mosque and I think the Prime Minister behaved completely appropriately in those circumstances, and we have expressed our devastation at what's happened."
Many Twitter users defended Ardern in response to Hopkins' comment.
One said: "Whatever the Prime Minister does will be immeasurably more welcome and useful than anything you have ever said."